[CRIU] [PATCH v8 06/15] files: new "used" files list introduced

[Stanislav Kinsburskiy]

26.05.2016 15:20, Kirill Tkhai пишет:
> В Ср, 16/03/2016 в 16:17 +0300, Stanislav Kinsburskiy пишет:
>> This list contains all per-process used file fdinfo's, sorted by fd
>> number.
>> Will be used to safely create new artificial file descriptors and
>> also allow
>> to recreate temporary descriptors with original number, if possible,
>> like
>> AutoFS tries to preserve original pipe write end descriptor, when it
>> was
>> closed.
>> This patch also adds a couple of simple helpers to find unused file
>> descriptor:
>> 1) fd_is_used() does exactly what it is named
>> 2) find_unused_fd() returns "hint_fd" if unused or last used
>> descriptor plus
>> one.
>>
>> Signed-off-by: Stanislav Kinsburskiy <skinsbursky at virtuozzo.com>
>> ---
>>   criu/files.c            |    3 +++
>>   criu/include/files.h    |   33 +++++++++++++++++++++++++++++++++
>>   criu/include/rst_info.h |    1 +
>>   3 files changed, 37 insertions(+)
>>
>> diff --git a/criu/files.c b/criu/files.c
>> index 8a7d85f..40bb13a 100644
>> --- a/criu/files.c
>> +++ b/criu/files.c
>> @@ -646,6 +646,8 @@ static int collect_fd(int pid, FdinfoEntry *e,
>> struct rst_info *rst_info)
>>   	else
>>   		collect_gen_fd(new_le, rst_info);
>>   
>> +	collect_used_fd(new_le, rst_info);
>> +
>>   	list_add_tail(&new_le->desc_list, &le->desc_list);
>>   	new_le->desc = fdesc;
>>   
>> @@ -686,6 +688,7 @@ int prepare_fd_pid(struct pstree_item *item)
>>   	pid_t pid = item->pid.virt;
>>   	struct rst_info *rst_info = rsti(item);
>>   
>> +	INIT_LIST_HEAD(&rst_info->used);
>>   	INIT_LIST_HEAD(&rst_info->fds);
>>   	INIT_LIST_HEAD(&rst_info->eventpoll);
>>   	INIT_LIST_HEAD(&rst_info->tty_slaves);
>> diff --git a/criu/include/files.h b/criu/include/files.h
>> index 5db6ab1..d38dbfd 100644
>> --- a/criu/include/files.h
>> +++ b/criu/include/files.h
>> @@ -67,6 +67,7 @@ struct fdinfo_list_entry {
>>   	struct list_head	desc_list;	/* To chain
>> on  @fd_info_head */
>>   	struct file_desc	*desc;		/* Associated
>> file descriptor */
>>   	struct list_head	ps_list;	/* To chain  per-
>> task files */
>> +	struct list_head	used_list;	/* To chain per-
>> task used fds */
>>   	int			pid;
>>   	futex_t			real_pid;
>>   	FdinfoEntry		*fe;
>> @@ -108,11 +109,43 @@ struct file_desc_ops {
>>   	char *			(*name)(struct file_desc *,
>> char *b, size_t s);
>>   };
>>   
>> +static inline void collect_used_fd(struct fdinfo_list_entry
>> *new_fle, struct rst_info *ri)
>> +{
>> +	struct fdinfo_list_entry *fle;
>> +
>> +	list_for_each_entry(fle, &ri->used, used_list) {
>> +		if (new_fle->fe->fd < fle->fe->fd)
>> +			break;
>> +	}
>> +
>> +	list_add_tail(&new_fle->used_list, &fle->used_list);
>> +}
>> +
>>   static inline void collect_gen_fd(struct fdinfo_list_entry *fle,
>> struct rst_info *ri)
>>   {
>>   	list_add_tail(&fle->ps_list, &ri->fds);
>>   }
>>   
>> +static inline bool fd_is_used(struct list_head *head, int fd)
>> +{
>> +	struct fdinfo_list_entry *fle;
>> +
>> +	list_for_each_entry(fle, head, used_list) {
>> +		if (fle->fe->fd == fd)
>> +			return true;
>> +	}
>> +
>> +	return false;
>> +}
>> +
>> +static inline unsigned int find_unused_fd(struct list_head *head,
>> int hint_fd)
>> +{
>> +	if ((hint_fd >= 0) && (!fd_is_used(head, hint_fd)))
>> +		return hint_fd;
>> +	/* Return last used fd +1 */
>> +	return list_entry(head->prev, typeof(struct
>> fdinfo_list_entry), used_list)->fe->fd + 1;
> What is guarantee that we have a space between the last fd and
> INT/UINT_MAX?
>

Frankly speaking, there is no garantee.

>> +}
>> +
>>   struct file_desc {
>>   	u32			id;		/* File id,
>> unique */
>>   	struct hlist_node	hash;		/* Descriptor
>> hashing and lookup */
>> diff --git a/criu/include/rst_info.h b/criu/include/rst_info.h
>> index b6d378e..562e2f0 100644
>> --- a/criu/include/rst_info.h
>> +++ b/criu/include/rst_info.h
>> @@ -27,6 +27,7 @@ struct fdt {
>>   struct _MmEntry;
>>   
>>   struct rst_info {
>> +	struct list_head	used;
>>   	struct list_head	fds;
>>   	struct list_head	eventpoll;
>>   	struct list_head	tty_slaves;
>>
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